Ultraviolet A light effectively reduces bacteria and viruses including coronavirus

PLoS One. 2020 Jul 16;15(7):e0236199. doi: 10.1371/journal.pone.0236199. eCollection 2020.


Antimicrobial-resistant and novel pathogens continue to emerge, outpacing efforts to contain and treat them. Therefore, there is a crucial need for safe and effective therapies. Ultraviolet-A (UVA) phototherapy is FDA-approved for several dermatological diseases but not for internal applications. We investigated UVA effects on human cells in vitro, mouse colonic tissue in vivo, and UVA efficacy against bacteria, yeast, coxsackievirus group B and coronavirus-229E. Several pathogens and virally transfected human cells were exposed to a series of specific UVA exposure regimens. HeLa, alveolar and primary human tracheal epithelial cell viability was assessed after UVA exposure, and 8-Oxo-2'-deoxyguanosine was measured as an oxidative DNA damage marker. Furthermore, wild-type mice were exposed to intracolonic UVA as an in vivo model to assess safety of internal UVA exposure. Controlled UVA exposure yielded significant reductions in Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli, Enterococcus faecalis, Clostridioides difficile, Streptococcus pyogenes, Staphylococcus epidermidis, Proteus mirabilis and Candida albicans. UVA-treated coxsackievirus-transfected HeLa cells exhibited significantly increased cell survival compared to controls. UVA-treated coronavirus-229E-transfected tracheal cells exhibited significant coronavirus spike protein reduction, increased mitochondrial antiviral-signaling protein and decreased coronavirus-229E-induced cell death. Specific controlled UVA exposure had no significant effect on growth or 8-Oxo-2'-deoxyguanosine levels in three types of human cells. Single or repeated in vivo intraluminal UVA exposure produced no discernible endoscopic, histologic or dysplastic changes in mice. These findings suggest that, under specific conditions, UVA reduces various pathogens including coronavirus-229E, and may provide a safe and effective treatment for infectious diseases of internal viscera. Clinical studies are warranted to further elucidate the safety and efficacy of UVA in humans.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis / radiation effects
  • Bacteria / radiation effects
  • Bacterial Infections / microbiology
  • Bacterial Infections / therapy*
  • Cell Survival / radiation effects
  • Colon / microbiology
  • Colon / radiation effects
  • Coronavirus 229E, Human / radiation effects
  • DNA Damage / radiation effects
  • Disease Models, Animal
  • Enterovirus B, Human / radiation effects
  • Female
  • HeLa Cells
  • Humans
  • Intestinal Mucosa / microbiology
  • Intestinal Mucosa / radiation effects
  • Male
  • Mice
  • Mycoses / microbiology
  • Mycoses / therapy*
  • Opportunistic Infections / microbiology
  • Opportunistic Infections / therapy*
  • Primary Cell Culture
  • Ultraviolet Therapy / adverse effects
  • Ultraviolet Therapy / methods*
  • Virus Diseases / therapy*
  • Virus Diseases / virology
  • Yeasts / radiation effects

Grants and funding

This project was partly funded by a grant to AR (award number 2017-494) from the Kenneth Rainin Foundation. It provided salary support for AR and GL. https://krfoundation.org/. The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. SS is an employee of Australian Clinical Labs. Australian Clinical Labs had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.